Diarrhea Flashcards
Clinical definition of diarrhea
Increase in frequency, volume, or urgency of defecation with or without a change in consistency
Normal stool frequency=
3 movements per week all the way up to 3 per day
Physiologic definition
more than 200 gm of stool per day
Normal input into the gut per day in liters
about 8.5…..only a quarter of this is from foodstuffs
of the 8.5 liters that comes into the small intestine, how much is absorbed
Most…about 7 liters. Of the remaining 1.5 liters that enters the colon about 1.4 liters is absorbed
What is the basis of normal fluid absorption
Na uptake
Two modes of Na uptake in the small intestine?
- Na/ glucose co-transporter
- Na/ H exchanger
FOUND IN THE VILLI….this is important because it shows that no villi = no fluid absorption
Large intestinal Na uptake occurs via?
Epithelial Na channel (ENac)
So diarrhea is increased intraluminal fluid that is a result of :
either decreased absorption or increased secretion…or both in some cases.
ALONG with Rapid Transit through GI
Osmotic diarrhea characteristics
ingestion of some solute that can’t be absorbed and therefore acts as an osmotic agent by drawing fluid into the gut lumen
Secretory diarrhea characterized by
Active secretion of electrolytes into the gut lumen
Inflammatory diarrhea characterized by
inflammatory mediators stimulate secretion and the tight junctions of the epithelial barrier become loose
see figures
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Osmotic diarrhea causes
- Non-absorbable carbs
- Non-absorbably electrolytes
- Malabsorption syndromes
The key to all secretory diarrhea is
excessive Cl- secretion into the gut
How does cholera work
- invades enterocytes via the apical membrane and then migrates to the basolateral membrane (blood side)
- activates adenylate cyclase which activates cAMP which opens up chloride channels so that chloride can move into lumen
- Also inhibits Na/H co-transporter so that the only route of Na absorption is the Na Glucose exchanger
- The oral rehydration formula is a high salt drink containing glucose. This allows it to exploit the Na/Glucose transporter
Volume of BM in secretory diarrhea?
High volume
Volume of BM in osmotic diarrhea
moderate
Which diarrhea resolves with fasting
Osmotic…b/c it is usually caused by something we eat
Which diarrhea has very low flatulence levels?
secretory…osmotic = high
stool pH in osmotic vs secretory
low pH in osmotic (below 5.3)
pH is 6-7 in secretory
Osmolar gap?
In secretory diarrhea, most of the osmoles are electrolytes so the osmolar gap is low. Remember, this is calculated by taking a stool sample and sending it off for Na+ and K+ levels, mult these by 2, and then subtract from 290. Since secretory diarrhea has a ton of electrolytes in the stool the osmolar gap should be less than 50. In osmotic diarrhea it will be over 125
Acute diarrhea time frame
less than 3 weeks
Cause of acute diarrhea is almost always
infectious
Acute diarrhea is generally always what type(s)
inflammatory or secretory
Prognosis of acute diarrhea
self-limited
Management of acute diarrhea
supportive
Most common causes of infectious diarrhea in the US
- Viral
- E. Coli
- Campylobacter
Some Shigella, salmonella,
Giardia from streams
Cryptosporidium (mostly AIDS pts)
C Dif
Third world causes
- Viral still
- Campylobacter
- E. Coli
CHOLERA
Entameba Histolytica
Salmonella and Shigella
Cryptosporidium (infants)
MCC is travellers diarrhea
E. Coli
Medical management of acute diarrhea
- No blood, no dehydration:
Probably viral. give fluid and pepto - No dehydration, blood +
Probably bacterial but often self limited,
Should do a stool sample. give fluids and pep - Dehydration with or without blood
Culture stool, IV fluids or oral rehydration form
anti- diarrheal agent - Bloody, dehydrated, septic
Culture, IV fluid, IV cipro
C. Diff risk factors
Antibiotic usage
Old age
hospitalization
Cause of C. Diff colitis
The Cytotoxins A and B
How do you diagnose C. Diff
Endoscopy- you will see the colitis
Stool assay for cytotoxins A and B
Treatment of C. Diff
stop the offending Antibiotic
Used metronidazole or vancomycin to treat
Use cholestryamin to bind the toxins
Lactase deficiency clinical features
- osmotic diarrhea
- they’ll have gas
- the stool will be acidic
bacterial overgrowth =
bacteria present in small bowel
What do bacteria in small bowel do to bile acid
unconjugate them, these unconjugated bile acids then move into the colon and cause secretory diarrhea
Microscopic Colitis types
Lymphocytic collits and Collagenous Collitis
Microscopic collitis presentation
chronic, watery, non-bloody diarrhea in adults
Behcet’s disease…KNOW
Generalized vasculitis which presents with oral and genital apthous ulcers, uveitis, GI tract ulcers, and non-erosive arthritis
Treat Behchets with
immunosuppresives
check out red flags slides at teh end
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